Diaphragm for sound-reproducers.



F. W.,THOMAS. DIAPHRAGM' FOR SOUND RBPRODUCERS.

APPLICATION FILED JULY so, 191s.

1,1 16,166. Patented N0v.3,1914.

Jjf, 1%-@ tory action.

' tical lv UNTE ey T FREDERCC lf?. THOMAS, NEVI CITY; NFi/V YRK.

Specification of Letters Patent.

la'tented Nov. 3519i@ Application tiled July 3G, 1913. Serial No. 'Zc'll corders and reiirodueers,

posed, and among; these vothers are nietallic diaphragins variously.' cori-ugated or indented for the pin-pose or" obtaining a production or recording of sounds equivam lent to that obtainable with niica, the aim being to olftain a cheap substitute, as f is expensive in the present condition oi? market. are unsatisfactory i'or vari/.ius reasons la mainly on account of their weakness at the Central part where buckling occurs, thus showing a lach of strength oit' material or required stillness. decor-ding to another type ol." diaphragm, the diaphraginfis i'lat throughout its area and the metal pounded to Strengthen the diaphragm lift coinpacting the nnitcriah and then the diaghrag'iu nickel-plated to prevent corrosion or ail'eetion liv the elements. Such inetal diaphragins lieing oi' the saine thickness from center to edge are ua, the lark of stillness at the renter7 ain therinore. because of the coating" o? i "hclplate, which inaterialljv interferes with IVhe tonal qualities.

lt is the. ol tiert oi the present invention to overcome the objections a'hove noted in* producing' a metallic diaphragm which in recording and reproducing qualities is superior to inica. Ytar less expensive. smaller in size Vlor the saine Capacity ot sound reproducing and recording, and which pracintles'trurtihle. ivhereas in'ica diaphragme are olA veri' short lite because of theiiflzin'iinated structure. which results in the separation ot the lamina@ h v the iihra44 In carrying; out the invei'ition able metal may lie einploved that callv unaffected by the weather any suitperature changes. such metals being gold,

Corrugated metallic diaihraggnls;

although numerous other types ol diaphragnis have been proi peripheryA by stamping the silver, platinum., antin^. onyy tin, aluminum and the lil e and alloys of such metals. Blanks cut. from sheets of metal and preferably in the forni of disks are subjected to a'pounding, hammering or other compressing or conipacting operation, whereby the metal is compacted and the air in the pores excluded. rEhe. pounding or hammering is so carried out tlat the resulting diaphragm will he o f somewhat greater thickness at the iniddlethan at the periphery, there being,` a gradual and uniform diminution of thiol;- ness from the center outwardly. furing the shaping of the diaphragm the metal spreads radially7 whereby the diaphragm ac- `vaires the required stillness or rigidity and entirely overcomes ani7 tendency to buckle. ln other Words, 'the diaphragnris ot unifornil'v increasing strength from the sup-V ported per eher;T to the unsupported cena mil' llylien the diaphragme' are niade of certain kinds of nietalseit has been found beneficial to suliject the diaphragm to bath of nid ot' potassium, which teinpers and strengthens the nietal.- lt may also necessary in some instances to increase the stift'- ness or rigidity of: the diaphragm, after it has hei-n acted on ivy the ponnding or lianiniering dies which produce the unitorni decrease in thiclvness from the center to thc entire peripheral portion ot the diaphraeni hy means ci? an annular die which' a fa`ial expansion and hence radr liet-anse otA the l'low oi metal outwardly radial tlireciors. For a more detailed understanding o he invention reference is to he had to the ac companyii'ig drawings taken in connection with the ivillowing description and the elaiins appended hereto.

is practil 1 and tera ln the acconipanying dra-wings, wherein similar reference characters designate corresponding` parts throughout the several viens. Figure l is a side view ot' a blank of metal ifi-oni which a diaphragm is made; Fig'. 2 a plan vieu thereof; Fig. 3 is a vir-vr showing the lilanl; in the initial stage heilig hammered; Fig. fl is similar vieu' slioivinfr the final stage ol pounding or hainnwringr the diaphragm; Fig. 5 is a view showing;` the manner olI compressing the peripheral portion of the hammered diaphragni; Fig'. is a plan view `of the diaphragm resulting from, the operation shown in Fig. 5: Fig. 'i' is a sectional View of the finished diaphragm having` one side and the other side convex; Fig. 8 is a sectional view of a diaphragm convex on both sides; and Fig. 9 is a sectional View of a diaphragm Which tapers from the center to the periphery on straight lines. p

In carrying out the inyention a circular metal blank A is cut out from a sheet of metal slightly smaller than the final diametrical size desired for the diaphragm, since in the pounding or hammering operation a blank expands in all directions from the center. This blank A, shown in Figs. 1 and 2, is placed on an anvil B, Fig. 3, and subjected to a pounding or hammering operation by nicnas of a die C, the under surface l of which is accurately shaped in such a manner as to give the desired final form or surface shape tov the diaphragm. the present instance the die in Fig. 3 is formed with a very shallow concavity, so that obviously in the beginning of the pounding operation the die will operate first on the entire periphery of the blank A. lll/lith the successive strokes the metal in the peripheral region of the diaphragm is compacted and expanded until fina-ily the entire blank is operated on by the die, as shown in Fig. Ll. This pounding of the metal greatly strengthens and stiiens the diaphragm so that buckling at the center is entirely overcome. This also is due tothe fact that there is a greater stock of metal at the center than at the periphery. rlrlhis'shaping of the diaghragm may be effected by a continuously applied pressure of the die C, or by a single stroke instead of by a repetition of blows, as in hammering.

. Should it be desired to impart greater stillness or rigidity to the diaphragm than is performed by the die C, the entire peripheral portion o'lf the diaphragm can be still further hammered to effect a uniform radial expansion from the center outwardly. To accomplish this an annular die D is ap plied to the periphery of the diaphragm A after being finished by the die C, and a blow or pressure is applied to the annular die i), so as to compress the diaphragm A to the saine degree throughout the entire periph# ery, the annular die being of such sir/:e as to have an engaging surface of about three thirty-seconds of an inch in radial dimensions.

instead of making the diaphragm dat on one side and convex on the other, as shown in Fig. T, the diaphragm can, by suitably working the blank` he made convex on both sides, as shown by thc diaphragm shown in Fig. 8. or as a further modification the diaphragm can be diminished in thinkncss from the center to the periphery along straight lines, as is shown by the diaphragm A3, Fig. 9. From this it' will he seen that the essential feature is that the diaphragm must be thickest at the center and decrease uniformly therefrom to the periphery, with its surfaces perfectly flat or iin/corrugated or unindented. As a specific illustration of the variation in thickness between the centri' and periphery of the finished diaphragm 'L may be stated that a diaphragm one incn and three-quarters in diameter has a thickness at the central partwhich' measures thirty-lire, according to a micrometer gage,`

While the thickness at the periphery should measure about thirty-sii; and one-half or thirty-seven micrometer gage. Such a diaphragm is stiilened equally at corresponding points considered from the center to the periphery, and the center isas strong as at any other point, so that there is no tendency to buckle. A hammered or pounded diaphragm made as described is capable of reproducing sounds Withthe same effect as amica diaphragm of larger size. F or instance, a diaphragm of one' and five-sism teenths inches 'under actual test is equiva# lent to a mica diaphragm of one and three quarters inches in diameter, While a metal diaphragm oi one and three-quarters inches in size is equivalent in reproducing quality to a mica diaphragm two and one-quarter inches in diameter.

lilith some kinds of metal it has been found beneficial to treat the diaphragm by giving vit a bath in cyanid el potassium, the effect orp which is to temper and strengthen the metal. Having thus described my invention, claim as neu7 and desire secure by Letters Patent:

l. rfthe herein-described method of making diaphragme for sound reproducers, reccrders, transmitters land receivers, which consists in subjecting a disk of metal lto a radially uniformly varying pressure whereby the diaphragm. is tensioned by thev radial flow of the metal.

The herein-described method or' making diaphragme for sound reproducers, recorders, transmitters andreceivers, which consists 'in placinr` a disk ot metal with one face on a fiat sui-race and snbjectii'ig the pposite face to a radially uniformly Varying pressure whereby the diaphragm is tensioncd by the radial don' of the metal.

Aln testimony whereof l have signed my name to this specification in the presenceA of tif-:o subscribing Witnesses.- 

